This invention relates to a stable aqueous hybrid binder containing colloidal silica, and the use thereof.
Colloidal silica have been used for a long time, e.g. as a coating material to improve adhesive properties as well as increasing wear and water resistance of various materials. However, these dispersions, especially highly concentrated colloidal silica dispersions, are liable to gelling or precipitation of silica, which makes longer storage impossible.
Colloidal silica in polymeric coatings can improve properties such as scratch resistance, UV protection or conductivity in a targeted manner. Control of the surface modification and dispersing of the colloidal silica determines the required transparent appearance of the coatings and properties thereof.
Various approaches have been pursued in the past for introduction of the colloidal silica into coating composition formulations. The colloidal silica can be mixed directly into the resin or curing agent component or into the coating composition ready for application. In aqueous systems there is the possibility of dispersing the colloidal silica in the aqueous phase. The in situ preparation of the colloidal silica in one of the binder components and adaptation of the surface to either the resin or the curing agent component have furthermore been described.
From the practical point of view, it is advantageous to disperse the colloidal silica as stable masterbatches in one of the components, so that a long-term storage stability and a simple ease of handling in the formulation of lacquers is ensured. In the end use, the colloidal silica must likewise be readily dispersible in a finely divided manner, so that advantageous properties such as transparency, scratch resistance or conductivity result.
In practice, the colloidal silica is conventionally dispersed into the resin component, into the aqueous phase or into the finished mixture of curing agent and resin shortly before curing. As a rule, for this it is necessary to adapt the surface of the colloidal silica to the specific matrix of the coating composition or of the adhesive. The disadvantage of simple mixing in of modified colloidal silica is the dependency of the stability on the complete formulation, i.e. on all the formulation constituents. Variation of one parameter can lead here to demixing (Pilotek, Steffen; Tabellion, Frank (2005), European Coatings Journal, 4, 170 et seq.).
US20090163618A1 claims aqueous binder dispersions based on silane-modified polymeric binders and inorganic nanoparticles, a process for the preparation thereof and the use thereof for the production of high quality coatings, in particular clear lacquers.
WO2001018081A1 claims a method for producing an aqueous dispersion of composite particles made up of polymerisate and fine inorganic solid material. According to said method, at least one ethylenically unsaturated monomer is dispersed in an aqueous medium and polymerised using at least one radical polymerisation initiator, in the presence of at least one dispersed, fine inorganic solid material and at least one dispersing agent, according to the radical aqueous emulsion polymerisation method.
The method in the prior art require special silanization for the polymer, or run in-situ polymerization in the presence of special dispersant.
It is therefore, still desired in the technical field, a new and simple processed stable colloidal silica containing polymeric binders, without modification, and to get to a novel coating composition, especially, aqueous coating composition that has more efficient stain resistance/removal function and also under a reasonable and controllable cost.